The field of invention relates to MR head technology generally; and more specifically, to seed layer structures that may be used to form a high sensitivity MR head.
Hardware systems often include memory storage devices having media on which data can be written to and read from. A direct access storage device (DASD or disk drive) incorporating rotating magnetic disks are commonly used for storing data in magnetic form. Magnetic heads, when writing data, record concentric, radially spaced information tracks on the rotating disks.
Magnetic heads also typically include read sensors that read data from the tracks on the disk surfaces. In high capacity disk drives, magnetoresistive (MR) read sensors, the defining structure of MR heads, can read stored data at higher linear densities than thin film heads. An MR head detects the magnetic field(s) through the change in resistance of its MR sensor. The resistance of the MR sensor changes as a function of the direction of the magnetic flux that emanates from the rotating disk.
One type of MR sensor, referred to as a giant magnetoresistive (GMR) effect sensor, takes advantage of the GMR effect. In GMR sensors, the resistance of the MR sensor varies with direction of flux from the rotating disk and as a function of the spin dependent transmission of conducting electrons between magnetic layers separated by a non-magnetic layer (commonly referred to as a spacer) and the accompanying spin dependent scattering within the magnetic layers that takes place at the interface of the magnetic and non-magnetic layers.
GMR sensors using two layers of magnetic material separated by a layer of GMR promoting non-magnetic material are generally referred to as spin valve (SV) sensors. In an SV sensor, one of the magnetic layers, referred to as the pinned layer, has its magnetization direction xe2x80x9cpinnedxe2x80x9d via the influence of exchange coupling with an antiferromagnetic layer. Due to the relatively high internal anisotropy field associated with the pinned layer, the magnetization direction of the pinned layer typically does not rotate from the flux lines that emanate/terminate from/to the rotating disk. The magnetization direction of the other magnetic layer (commonly referred to as a free layer), however, is free to rotate with respect to the flux lines that emanate/terminate from/upon the rotating disk.
xe2x80x9cBottomxe2x80x9d spin valves are spin valves having an antiferromagnetic layer formed prior to the formation of free layer. FIG. 1 shows a prior art SV sensor 100 comprising a seed layer 102 formed upon a gap layer 101. The sensor 100 of FIG. 1 is formed, layer by layer in the +x direction. Over seed layer 102 is an antiferromagnetic (AFM) layer 103. The seed layer 102 helps properly form the microstructure of the antiferromagnetic (AFM) layer 103. The AFM layer 103 is used to pin the magnetization direction of the pinned layer 104. Pinned layer 104 is separated from free layer 105 by the non magnetic, GMR promoting, spacer layer 119. Note that free magnetic layer 105 may be a multilayer structure having two or more ferromagnetic layers.
FIG. 2 shows another prior art xe2x80x9cbottomxe2x80x9d SV sensor structure 200 where the pinned layer is implemented as a structure 220 having two ferromagnetic films 221, 222 (also referred to as MP2 and MP1 layers, respectively) separated by a non ferromagnetic film 223 (such as ruthenium Ru) that provides antiparallel coupling of the two ferromagnetic films 221, 222. Sensor structures such as that 200 shown in FIG. 2 are referred to as AP sensors in light of the antiparallel magnetic relationship between films 221, 222. Similarly, structure 220 may also be referred to as an AP layer 220.
FIG. 2 shows an AP sensor 200 comprising a seed layer 202 formed upon a gap layer 201. Over seed layer 202 is an antiferromagnetic (AFM) layer 203. The seed layer 202 helps properly form the microstructure of AFM layer 203. The antiferromagnetic (AFM) 203 layer used to pin the magnetization direction of the MP2 layer 221. MP1 layer 222 is separated from free layer 205 by spacer layer 204. Note that free layer 205 may be a multilayer structure having two or more ferromagnetic layers.
Problems with forming the bottom sensors 100, 200 shown in FIGS. 1 and 2 include forming a seed layer 102, 202 with a microstructure that suitably influences the microstructure of the AFM layer 103, 203.
An apparatus is described comprising a seed layer between a gap layer and an Iridium Manganese (IrMn) antiferromagnetic layer. The seed layer comprises an oxide layer next to a magnetic layer.